getAzimuth

Get the azimuth of a point with regards to the topocentric frame center point.

The azimuth is the angle between the North direction at local point and
the projection in local horizontal plane of the direction from local point
to given point. Azimuth angles are counted clockwise, i.e positive towards the East.

computeLimitVisibilityPoint

Compute the limit visibility point for a satellite in a given direction.

This method can be used to compute visibility circles around ground stations
for example, using a simple loop on azimuth, with either a fixed elevation
or an elevation that depends on azimuth to take ground masks into account.